package cn.bugstack.springframework.context.event;

import cn.bugstack.springframework.beans.BeansException;
import cn.bugstack.springframework.beans.factory.BeanFactory;
import cn.bugstack.springframework.beans.factory.BeanFactoryAware;
import cn.bugstack.springframework.beans.factory.BeanNameAware;
import cn.bugstack.springframework.beans.factory.support.SimpleInstantiationStrategy;
import cn.bugstack.springframework.beans.utils.ClassUtils;
import cn.bugstack.springframework.context.ApplicationEvent;
import cn.bugstack.springframework.context.ApplicationListener;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.Set;

public abstract class AbstractApplicationEventMulticaster implements ApplicationEventMulticaster, BeanFactoryAware {
    public final Set<ApplicationListener<ApplicationEvent>> applicationListeners=new LinkedHashSet<>();

    private BeanFactory beanFactory;

    @Override
    public void addApplicationListener(ApplicationListener<?> listener) {
        applicationListeners.add((ApplicationListener<ApplicationEvent>) listener);
    }

    @Override
    public void removeApplicationListener(ApplicationListener<?> listener) {
        applicationListeners.remove(listener);
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        this.beanFactory = beanFactory;
    }

    protected Collection<ApplicationListener> getApplicationListeners(ApplicationEvent event){
        LinkedList<ApplicationListener> allListeners = new LinkedList<>();
        for (ApplicationListener<ApplicationEvent> listener : applicationListeners) {
            if (supportsEvent(listener,event)) allListeners.add(listener);
        }
        return allListeners;
    }

    /**
     * 监听器是否对该事件感兴趣
     */
    protected boolean supportsEvent(ApplicationListener<ApplicationEvent> applicationListener,ApplicationEvent event){
        Class<? extends ApplicationListener> listenerClass = applicationListener.getClass();
        // 按照 CglibSubclassingInstantiationStrategy、SimpleInstantiationStrategy 不同的实例化类型，需要判断后获取目标 class
        Class<?> targetClass= ClassUtils.isCglibProxyClass(listenerClass) ? listenerClass.getSuperclass():listenerClass;
        Type genericInterface = targetClass.getGenericInterfaces()[0];

        Type actualTypeArgument = ((ParameterizedType) genericInterface).getActualTypeArguments()[0];
        String className = actualTypeArgument.getTypeName();
        Class<?> eventClassName;
        try{
            eventClassName=Class.forName(className);
        }catch (ClassNotFoundException e){
            throw new BeansException("Wrong event class name: "+className);
        }
        // 判定此 eventClassName 对象所表示的类或接口与指定的 event.getClass() 参数所表示的类或接口是否相同，或是否是其超类或超接口。
// isAssignableFrom 是用来判断子类和父类的关系的，或者接口的实现类和接口的关系的，默认所有的类的终极父类都是 Object。如果 A.isAssignableFrom(B)结果是 true，证明 B 可以转换成
// 为 A,也就是 A 可以由 B 转换而来。
        return eventClassName.isAssignableFrom(event.getClass());
    }
}
